Method and apparatus for expanding tobacco material

ABSTRACT

A tobacco material expansion method includes the steps of wetting and swelling a tobacco material by bringing the tobacco material into contact with a water vapor stream at 100 to 160° C., and drying the tobacco material by bringing the wetted swelled tobacco material into contact with a superheated water vapor stream at a temperature higher than that of the water vapor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of PCT Application No.PCT/JP2011/058340, filed Mar. 31, 2011, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for expanding atobacco material.

2. Description of the Related Art

A tobacco material (for example, midribs) is separated from tobaccoleaves, and occupies 20 to 30 wt % of tobacco leaves. Cut midribs (cutstem) are used in cut tobacco together with cut lamina from whichmidribs are removed in order to effectively use the tobacco material.The cut midribs are generally obtained by rolling and cutting midribs.An expansion process is performed on the cut midribs by humidificationand drying, in order to increase the filling capacity andcombustibility, and relax the smoke flavor. The conventional cut midribexpansion processes and related techniques will be explained below.

A method and apparatus for applying a conditioning agent to the tobaccomaterial are disclosed in Japanese Patent No. 4031115. This apparatushas a structure in which a nozzle hole is attached to a protrusion, forexample, a band-line pin, such as an impeller having a rotatingwinnowing roll (to be referred to as a winnower hereinafter). In thismethod, a conditioning agent spraying process of spraying steam againsta freely falling tobacco material from the nozzle is performed beforedrying by using the above-mentioned apparatus. After that, the tobaccomaterial is conveyed to a drying process zone.

A method and apparatus for expanding the tobacco material are disclosedin U.S. Pat. No. 4,766,912. This apparatus includes a steam spray deviceand fluidized bed dryer which include a vibrating conveyor for conveyingthe tobacco material, and convey the tobacco material while vibratingthe conveyed tobacco material and spraying steam against the materialthrough holes formed in the lower surface of the vibrating conveyor,thereby increasing the filling capacity of the tobacco material. Inconnection with this U.S. patent, an apparatus including a closedtransport pipeline formed as a vibrating conveyor having an inlet andoutlet, a supply device for supplying steam or a heated gas to thebottom portion of this transport pipeline, and a spray hole is disclosedin U.S. Pat. No. 2,802,334.

A method and apparatus for a tobacco drying process of continuouslyperforming a two-step stream drying process are disclosed in Jpn. Pat.Appln. KOKAI Publication No. 62-3778. That is, the tobacco material issupplied into a high-temperature gas medium and transferred to a firstseparator through a first duct, thereby separating the material and gasmedium. The high-temperature gas medium is supplied to a second duct,and the separated tobacco material is supplied downstream of the firstseparator. The tobacco material and high-temperature gas medium aretransferred to a second separator through the second duct, and separatedfrom each other. By thus passing the material and medium through twodrying zones, it is possible to 1) shorten the time during which thetobacco material is continuously exposed to the high-temperature gasmedium, 2) eliminate the occurrence of excessively concentratedoverheating, and 3) increase the drying efficiency by the relativevelocity difference because the tobacco material is accelerated in twosteps. The use of a separator for shortening the time during which thetobacco material and high-temperature gas medium are in contact witheach other is also described.

Unfortunately, the above-described related arts have the followingproblems.

In Japanese Patent No. 4031115, the passing time of the tobacco materialand steam in the apparatus is short from the description of thefree-fall velocity, the effective height of the apparatus, and therotational speed (200 rpm) of the winnower. Since the contact time ofthe tobacco material and steam is short, therefore, wetting and swellingare not sufficiently performed. Also, the parts of the winnowerdeteriorate rapidly because the winnower has the rotating portion.Furthermore, the tobacco material is readily twined around the rotatingportion. The twined tobacco material exerts a large influence on thesmoke flavor and physical properties.

In U.S. Pat. No. 4,766,912, the steam spray device has the structurethat conveys the material by vibration, and sprays steam from the holesin the bottom surface of the vibrating conveyor. This decreases thedurability because driving parts deteriorate rapidly due to vibration.Also, steam is sprayed from the bottom surface of the vibrating conveyorby using pores having a diameter of, for example, 0.8 mm. Therefore, thepores are clogged with a scale (an inorganic material such as calciumcarbonate) contained in the steam and fine powder of the tobaccomaterial. This clogging of the pores fluctuates the steam amount,thereby making the quality of the processed tobacco material unstable.

In Jpn. Pat. Appln. KOKAI Publication No. 62-3778, the two-step streamdrying process is performed using the two separators connected inseries, so drying of the tobacco material progresses in each step.However, the characteristics of the apparatus extremely shorten thecontact time of the tobacco material and the high-temperature wet air orsuperheated steam flow. This makes it difficult to sufficiently wet orswell the tobacco material. In addition, the tobacco material isdeposited on a mesh screen of the separator, and closes an exhaustsystem. This interferes with the continuous operation of the separator.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a tobacco material expansion methodcapable of increasing the filling capacity of a tobacco material whencompared to the conventional methods.

The present invention provides a tobacco material expansion apparatuscapable of increasing the filling capacity of a tobacco material whencompared to the conventional methods, and having a simple structure thatimplements continuous processing and high durability.

According to the first aspect of the present invention, there isprovided a tobacco material expansion method including the steps ofwetting and swelling a tobacco material by bringing the tobacco materialinto contact with a water vapor stream at 100 to 160° C., and drying thewetted swelled tobacco material by bringing the tobacco material intocontact with a superheated water vapor stream at a temperature higherthan that of the water vapor.

According to the second aspect of the present invention, there isprovided a tobacco material expansion apparatus including a firstcyclone including an inlet, an exhaust port, and an outlet, a firstsupply-side duct connected to the inlet of the first cyclone, a firstexhaust-side duct connected to the exhaust port of the first cyclone, afirst water vapor supply unit connected to the first supply-side duct, afirst tobacco material supply unit connected to the first supply-sideduct positioned between a connecting portion of the first water vaporsupply unit and the inlet of the first cyclone, a second cycloneincluding an inlet, an exhaust port, and an outlet, a second supply-sideduct connected to the inlet of the second cyclone, a second exhaust-sideduct connected to the exhaust port of the second cyclone, a heatingmember placed in the second supply-side duct, a second water vaporsupply unit connected to the second supply-side duct positioneddownstream of the heating member, a second tobacco material supply unitconnected to the second supply-side duct positioned between the inlet ofthe second cyclone and the heating member, and a conveyor memberconfigured to convey the tobacco material discharged from the outlet ofthe first cyclone to the second tobacco material supply unit.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The single FIGURE is a schematic view showing a tobacco materialexpansion apparatus according to an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

A tobacco material expansion method according to an embodiment of thepresent invention will be explained below.

(First Step)

A tobacco material is wetted and swelled by bringing it into contactwith a water vapor stream at 100 to 160° C.

As the tobacco material, it is possible to use, for example, cutmidribs. The cut midribs can be obtained by separating rod-like midribsfrom tobacco leaves, and rolling and cutting the rod-like midribmaterial in accordance with the conventional methods. More specifically,the rod-like midrib material is humidified to have a water content of,for example, 15 to 50 wt %, and preferably, 20 to 40 wt %. Thehumidified rod-like midrib material is rolled by a rolling mill having aroll distance of, for example, 0.5 to 1.2 mm, and shredded into a widthof 0.1 to 0.3 mm, thereby forming cut midribs.

Since the water vapor has a temperature of 100 to 160° C., the tobaccomaterial can be wetted and swelled without being dried. The water vaportemperature is more preferably 110 to 150° C.

The tobacco material can be brought into contact with the water vaporstream by, for example, rotating the tobacco material together with thewater vapor stream. This rotation can be performed by using, forexample, a cyclone. The residence time during the rotation is preferably0.5 to 5 s.

When the tobacco material is brought into contact with the water vaporstream at the above-mentioned temperature for the abovementionedresidence time, condensation heat transfer of the water vapor to thetobacco material occurs. This condensation heat transfer raises thewater content and temperature (temperature of goods) of the tobaccomaterial, and softens the tobacco texture, thereby causing wetting andswelling. When the tobacco material is brought into contact with thewater vapor stream at the aforementioned temperature for theaforementioned residence time, the wetted swelled tobacco material isnot dried, and the water content of the tobacco material is equal to orincreases by 5 wt % or less from that before the tobacco material isbrought into contact with the water vapor stream.

(Second Step)

The wetted swelled tobacco material is dried by bringing it into contactwith a superheated water vapor stream at a temperature higher than thatof the water vapor in the first step, thereby expanding the tobaccomaterial.

Since the superheated water vapor has a temperature higher than that ofthe water vapor in the first step, the wetted swelled tobacco materialcan efficiently be dried. The superheated water vapor has a temperaturehigher than that of the water vapor in the first step, and preferablyhas a temperature range of 160 to 280° C. For example, when thetemperature of the superheated water vapor is 160° C., the water vaportemperature in the first step is set at a temperature lower than 160°C., thereby making the temperature of the superheated water vapor higherthan the water vapor temperature. The temperature of the superheatedwater vapor is more preferably 180 to 270° C.

The wetted swelled tobacco material can be brought into contact with thesuperheated water vapor stream by using various existing methods. It isparticularly favorable to rotate the tobacco material together with thesuperheated water vapor stream. This rotation can be performed by using,for example, a cyclone. The residence time during the rotation ispreferably 2 to 15 s.

In the abovementioned drying step, the water content of the tobaccomaterial can be reduced to, for example, 3 to 15 wt %.

In this embodiment, the tobacco material can be re-humidified after thedrying step. This re-humidification can be performed by, for example,spraying water against the tobacco material. The re-humidification isdesirably executed on the tobacco material having a water content of 10wt % or less.

In the tobacco material expansion method according to the embodimentexplained above, the tobacco material is first brought into contact witha water vapor stream at 100 to 160° C. This makes it possible tosufficiently wet and swell the texture of the tobacco material (forexample, cut midribs) in a state in which the water content of thehumidified tobacco material is maintained or increased by 5 wt % orless, i.e., in an undried state. After that, the wetted swelled tobaccomaterial is dried by bringing it into contact with a superheated watervapor stream at a temperature higher than that of the water vapor in theabove step, preferably, within a temperature range of 160 to 280° C.Consequently, it is possible to obtain an expanded tobacco material (forexample, expanded cut midribs) having filling capacity higher than thatobtained when a humidified tobacco material is directly dried withsuperheated water vapor by the conventional method. By making the watercontent of the dried tobacco material lower than 12 wt %, it is possibleto obtain an expanded tobacco material having a greatly increasedfilling capacity.

Especially when bringing the tobacco material into contact with thewater vapor stream in the wetting/swelling step, the tobacco material isrotated together with the water vapor stream. This can further increasethe wettability and swellability of the tobacco material withoutdamaging it.

Also, when bringing the tobacco material into contact with thesuperheated water vapor stream in the drying step, the wetted swelledtobacco material is rotated together with the superheated water vaporstream. Consequently, it is possible to more efficiently dry the tobaccomaterial without damaging it.

In the embodiment, the tobacco material (having a water content of, forexample, 10 wt % or less) after the drying step is furtherre-humidified, for example, re-humidified to have a water content of 12wt %. This makes it possible to obtain an expanded tobacco materialhaving filling capacity higher than that obtained by directly drying thehumidified tobacco material with superheated water vapor such that thewater content is 12 wt %. This is so because when the tobacco materialis dried to have a low water content once, the rigidity of the tobaccomaterial texture (for example, the midrib texture) increases, so theexpanded state can strongly be fixed, and the texture of the expandedtobacco material hardly shrinks even when the material is re-humidified.

Next, the tobacco material expansion apparatus according to theembodiment will be explained with reference to FIG. 1.

A first cyclone 1 has an inlet 2 in the sidewall, an exhaust port 3 inthe upper portion, and an outlet 4 in the bottom portion. A firstcirculation duct 5 has one end connected to the inlet 2 of the firstcyclone 1, and the other end connected to the exhaust port 3 of thefirst cyclone 1.

A check valve 6 is attached to the first circulation duct 5 so as to bepositioned near the middle of the length of the first circulation duct5. The check valve 6 lets a water vapor stream flow in the firstcirculation duct 5 from the exhaust port 3 to the inlet 2 of the firstcyclone 1, and restricts a flow in the opposite direction. A firstheater 7 is attached to a portion of the first circulation duct 5, whichis positioned between the check valve 6 and the inlet 2 of the firstcyclone 1.

A first water vapor supply pipe 8 is connected to a portion of the firstcirculation duct 5, which is positioned between the check valve 6 andfirst heater 7. The first water vapor supply pipe 8 has an open/closevalve 9 for regulating the water vapor supply amount. A first tobaccomaterial supply unit 10 is connected, via a first air lock 11, to aportion of the first circulation duct 5, which is positioned between thefirst heater 7 and the inlet 2 of the first cyclone 1. A drain separator12 and exhaust fan 13 are arranged in the first circulation duct 5 inthis order from the exhaust port 3 of the first cyclone 1 toward thecheck valve 6.

The outlet 4 of the first cyclone 1 is connected to a first dischargeduct 14. A second air lock 15 is inserted into the first discharge duct14.

A second cyclone 21 is installed adjacent to the first cyclone 1. Thesecond cyclone 21 has an inlet 22 in the sidewall, an exhaust port 23 inthe upper portion, and an outlet 24 in the bottom portion. A secondcirculation duct 25 has one end connected to the inlet 22 of the secondcyclone 21, and the other end connected to the exhaust port 23 of thesecond cyclone 21.

A circulation fan 26 and a second heater 27 as a heating member arearranged in the second circulation duct 25 in this order from theexhaust port 23 toward the inlet 22 of the second cyclone 21, i.e., in adirection in which a superheated water vapor stream flows. An exhaustduct 28 is connected to a portion of the second circulation duct 25,which is positioned between the circulation fan 26 and second heater 27.The exhaust duct 28 exhausts the superheated water vapor stream flowingin the second circulation duct 25 as needed. The exhaust duct 28 has anopen/close valve 29 for regulating the exhaust amount.

A second water vapor supply pipe 30 is connected to a portion of thesecond circulation duct 25, which is positioned between the connectingportion of the exhaust duct 28 and the second heater 27. The secondwater vapor supply pipe 30 has an open/close valve 31 for regulating thewater vapor supply amount. A second tobacco material supply unit 32 isconnected, via a third air lock 33, to a portion of the secondcirculation duct 25, which is positioned between the second heater 27and the inlet 22 of the second cyclone 21. A conveyor member 34 has oneend positioned near the first discharge duct 14 of the first cyclone 1,and the other end positioned near the second tobacco material supplyunit 32. The conveyor member 34 conveys the tobacco material dischargedfrom the first cyclone 1 to the second tobacco material supply unit 32.

The outlet 24 of the second cyclone 21 is connected to a seconddischarge duct 35. A fourth air lock 36 is inserted into the seconddischarge duct 35.

A connection duct 37 connects a portion of the first circulation duct 5,which is positioned near the exhaust fan 13, to a portion of the secondcirculation duct 25, which is positioned near the exhaust port 23 of thesecond cyclone 21. A diaphragm valve 38 is attached to the connectionduct 37. A pressure gauge 39 is connected to a portion of the connectionduct 37, which is positioned between the diaphragm valve 38 and secondcirculation duct 25. The opening of the diaphragm valve 38 is controlledbased on pressure detection data (a pressure detection signal) from thepressure gauge 39.

The tobacco material expansion method using the tobacco materialexpansion apparatus shown in FIG. 1 described above will now beexplained.

First, a tobacco material (for example, cut midribs) is prepared. Thecut midribs are obtained by humidifying a rod-like midrib material tohave a water content of 15 to 50 wt % (wet material basis), rolling thehumidified material by a rolling mill having a roll distance of 0.5 to1.2 mm, and cutting the rolled material into a width of 0.1 to 0.3 mm.

Dried saturated water vapor is sprayed from the first water vapor supplypipe 9 to the first circulation duct 5 at a gauge pressure of 1 to 7bars. Note that the water vapor stream is heated by the first heater 7of the first circulation duct 5 as needed. After that, theabovementioned cut midribs are continuously supplied from the firsttobacco material supply unit 10 to the first circulation duct 5 throughthe first air lock 11. By driving the exhaust fan 13 beforehand, the cutmidribs flow together with the water vapor stream at a temperature of100 and 160° C. from the first circulation duct 5 into the first cyclone1, and rotate together with the water vapor stream. In this state, thewater content of the cut midribs is equal to or increases by 5 wt % fromthat before the supply, i.e., the cut midribs are sufficiently wettedand swelled. The time of circulation in the first circulation duct 5 androtation in the first cyclone 1 is preferably, for example, 0.5 to 5 s.

After the rotation, the cut midribs are separated from the water vaporstream. The separated cut midribs are discharged from the firstdischarge duct 14 connected to the first output 14 of the first cyclone1 to the conveyor member 34 through the second air lock 15. On the otherhand, the water vapor stream is discharged from the first exhaust hole 3of the first cyclone 1 to the first circulation duct 5 by driving theexhaust fan 13, and circulated toward the first inlet 2. In thiscirculation of the water vapor stream, water condensed in the watervapor stream is discharged from the drain separator 12.

The wetted cut midribs are conveyed to the second tobacco materialsupply unit 32 by the conveyor member 34, and supplied to the secondcirculation duct 25 through the third air lock 33. Saturated water vaporis sprayed from the second water vapor supply pipe 30 to the secondcirculation duct 25, and heated while passing through the second heater27, thereby forming a superheated water vapor stream at a temperaturehigher than the temperature of the water vapor supplied to the firstcyclone 1, and falling within the temperature range of 160 to 280° C. Bydriving the circulation fan 26 beforehand, the wetted cut midribssupplied to the second circulation duct 25 flow together with thesuperheated water vapor stream from the second circulation duct 25 intothe second cyclone 21, and rotate together with the superheated watervapor stream. In this state, the wetted cut midribs are dried andexpanded. The time of the circulation in the second circulation duct 25and the rotation in the second cyclone 21 is preferably, for example, 2to 15 s.

The rotated cut midribs (expanded cut midribs) are separated from thesuperheated water vapor stream. The separated expanded cut midribs aredischarged and collected, through the fourth air lock 36, from thesecond discharge duct 35 connected to the second outlet 24 of the secondcyclone 21. On the other hand, the superheated water vapor stream isexhausted from the second exhaust port 23 of the second cyclone 21 tothe second circulation duct 25 by driving the circulation fan 26, andcirculated toward the second inlet 22.

The water content of the obtained expanded cut midribs is 3 to 15 wt %.Also, the filling capacity of the expanded cut midribs is 5.8 to 7.5cc/g. Therefore, when compared to the filling capacity (4.5 cc/g) of theundried cut midribs immediately after cutting, the filling capabilitycan be increased by about 30 to 70%.

In the humidifying and drying processes of the cut midribs as describedabove, the opening of the diaphragm valve 38 attached to the connectionduct 37 is controlled based on the pressure detection data (pressuredetection signal) from the pressure gauge 39, and a desired amount of awater vapor stream flowing through the first circulation duct 5 issupplied to the second circulation duct 25 through the connection duct37 and used as a part of the superheated water vapor.

Note that in the cut midrib drying step performed by the system of thesecond cyclone 21 and second circulation duct 25, if the water contentbecomes, for example, 10 wt % or less, the cut midribs can bere-humidified by a well-known method such as water spraying.

In the tobacco material expansion apparatus according to the embodimentas explained above, a tobacco material (for example, cut midribs) iswetted and dried by using the first and second cyclones 1 and 21, andthe first and second circulation ducts 5 and 25 respectively connectedto the first and second cyclones 1 and 21. This makes it possible toincrease the opportunity of contact between the cut midribs and watervapor stream or superheated water vapor stream, without damaging the cutmidribs. Consequently, it is possible to efficiently wet and swell thecut midribs, and efficiently dry the cut midribs after that.Accordingly, expanded cut midribs having an increased filling capacitycan be obtained.

Also, the first and second cyclones 1 and 21 and first and secondcirculation ducts 5 and 25 incorporated into the expansion apparatushave extremely simplified structures, require neither a rotating partnor a mesh screen unlike the conventional apparatuses, and hence havehigh durability. This makes it possible to continuously wet and dry thecut midribs.

Furthermore, when the first and second circulation ducts 5 and 25 areconnected by the connection duct 37, the water vapor circulating in thefirst circulation duct 5 can effectively be used as a part of thesuperheated water vapor in the second circulation duct 25, and this canimplement an energy-saving operation.

Examples of the present invention will be explained in detail below byreferring to the tobacco material expansion apparatus shown in FIG. 1.

Example 1 Comparative Example

In Example 1, the drying step was performed using the system of thesecond cyclone and second circulation duct shown in FIG. 1.

First, a rod-like midrib material obtained by mixing 70 wt % offlue-cured tobacco and 30 wt % of burley tobacco was humidified to havea water content of 37 wt % by a method known to those skilled in theart, for example, spraying of water or water vapor. This rod-likemidribs were rolled by a pair of rollers having a distance of 0.8 mm,and shredded into a width of 0.2 mm, thereby preparing cut midribs as atobacco material.

Saturated water vapor was supplied at a flow rate of 40 kg/hr from thesecond water vapor supply pipe 30 to the second circulation duct 25(diameter: about 100 mm, length: about 22 m), and heated while passingthrough the second heater 27. The humidified cut midribs werecontinuously supplied at a flow rate of 25 kg/hr on humidified weightbasis from the second tobacco material supply unit 32 to the secondcirculation duct 25 through the third air lock 33. In this state, thewater vapor stream circulating through the second circulation duct 25was saturated water vapor having a vapor ratio of 90 vol % (an almostsuperheated water vapor stream), a flow velocity of 25 m/s, atmosphericpressure, and a temperature of 260° C. By driving the circulation fan 26beforehand, the humidified cut midribs were supplied together with thesuperheated water vapor stream from the second circulation duct 25 intothe second cyclone (diameter: about 460 mm, separator effective height:1.4 m), and dried and expanded by rotating together with the superheatedwater vapor stream. The residence time during the rotation was 5 s.

Examples 2 & 3 Comparative Examples

Humidified cut midribs were dried and expanded following the sameprocedures as in Example 1, except that the temperature of thesuperheated water vapor stream circulating together with the humidifiedcut midribs in the second circulation duct 25 was set at 230 and 210° C.

Example 4 Example

In Example 4, the above-described tobacco material expansion apparatusshown in FIG. 1 was used.

Humidified cut midribs (water content: 37 wt %, width: 0.2 mm) havingundergone the same processes as in Example 1 were prepared.

Saturated water vapor having a gauge pressure of 5 bars was sprayed at aflow rate of about 20 kg/hr from the nozzle portion (diameter=3 mm) ofthe first water vapor supply pipe 8 to the first circulation duct 5(diameter: about 250 mm, length: about 0.6 m) set in a horizontal state.The humidified cut midribs were continuously supplied at a flow rate of36 kg/hr on humidified weight basis from the first tobacco materialsupply unit 10 to the first circulation duct 5 through the first airlock 11. In this state, the water vapor stream circulating in the firstcirculation duct 5 was saturated water vapor at a temperature of 125° C.By driving the circulation fan 13 beforehand, the humidified cut midribswere supplied together with the water vapor stream from the firstcirculation duct 5 into the first cyclone 1 (diameter: about 50 mm,separator effective height: about 0.75 m), and wetted and swelled byrotating together with the water vapor stream. The time of passingthrough the first circulation duct 5 and first cyclone 1 (residencetime=1.5 s) was about 1.8 s. The water content of the wetted cut midribswas 39 wt %, i.e., increased by 2 wt % from the water content (37 wt %)when the material was humidified.

Then, the humidified cut midribs discharged from the first cyclone 1were continuously supplied to the second circulation duct 25 via theconveyor member 34 and second tobacco material supply unit 32, and driedand expanded with a superheated water vapor stream by using the secondcirculation duct 25 and second cyclone 21 under the same conditions asin Example 1 descried above. Note that the temperature of thesuperheated water vapor was set at 270° C.

Examples 5 & 6 Examples

Humidified cut midribs were dried and expanded following the sameprocedures as in Example 4, except that the temperature of thesuperheated water vapor stream circulating together with the humidifiedcut midribs in the second circulation duct 25 was set at 240 and 220° C.

The obtained expanded cut midribs of Examples 1 to 6 were stored(matched) in a constant-temperature and constant-humidity chamber at atemperature of 22.0° C. and a relative humidity of 60% for a week,thereby obtaining an equilibrium water content. After that, the fillingcapacity was measured.

The filling capacity indicates the filling capability of tobacco shredsin a smokable cigarette form. This measurement was performed usingDD-60A available from Borgwaldt, Germany. The experiment was conductedby repetitively measuring the filling capacity of the expanded cutmidribs five times, and calculating the average value.

Also, about 2 g of the expanded cut midribs were placed in a weighingbottle, and dried for 1 hour in a natural convection oven at atemperature of 100° C. After that, the water content of the expanded cutmidribs was calculated from the weight difference before and after thedrying, and obtained as the average value of five points.

Table 1 below shows the filling capacity and water content of theexpanded cut midribs of each of Examples 1 to 6.

TABLE 1 Presence/absence and Superheated water water vapor temperaturevapor temperature Water content (wt %) of shredded midribs Bulkiness ofwetting process during drying (° C.) During humidification After drying(cc/g) Example 1 Absent 260 37.0 5.4 6.2 Example 2 Absent 230 37.0 8.25.7 Example 3 Absent 210 37.0 11.0 5.4 During wetting After dryingExample 4 Present (150° C.) 270 39.0 4.7 7.3 Example 5 Present (150° C.)240 39.0 8.0 6.6 Example 6 Present (150° C.) 220 39.0 11.0 6.5

As shown in Table 1, the filling capacity increased (improved) by 1.0cc/g or more in each of Examples 4 to 6 in which the humidified cutmidribs were wetted with water vapor at a temperature of 125° C. beforebeing dried with a superheated water vapor stream, when compared toExamples 1 to 3 in which the humidified cut midribs were not wetted witha water vapor stream before being dried with a superheated water vaporstream. When represented by a ratio, a filling capacity of 1.0 cc/g ormore as described above is equivalent to about 20%. Since the fillingcapacity of unprocessed cut midribs before drying (after humidificationand cutting) was 4.5 cc/g, the expansion ratio increased to 62% in, forexample, Example 4, indicating that the expansion method was excellent.

Example 7 Example

In Example 7, the above-described tobacco material expansion apparatusshown in FIG. 1 was used.

Humidified cut midribs (water content: 37.0 wt %, width: 0.2 mm) havingundergone the same processes as in Example 1 were prepared.

The humidified cut midribs were wetted and swelled by using the firstcirculation duct 5 and first cyclone 1 under the same conditions as inExample 4. The water content of the wetted cut midribs was 39.0 wt %,i.e., increased by 2 wt % from the water content (37.0 wt %) when thematerial was humidified.

Then, the wetted cut midribs discharged from the first cyclone 1 werecontinuously supplied to the second circulation duct 25 via the conveyormember 34 and second tobacco material supply unit 32, and dried andexpanded with a superheated water vapor stream (temperature: 270° C.) byusing the second circulation duct 25 and second cyclone 21 under thesame conditions as in Example 1 described above.

After that, the expanded cut midribs were re-humidified by sprayingwater so that the water content was 12.5 wt %.

Example 8 Example

Wetted cut midribs were dried and expanded following the same proceduresas in Example 7, except that the temperature of the superheated watervapor stream circulating together with the wetted cut midribs in thesecond circulation duct 25 was set at 250° C. After that, the expandedcut midribs were re-humidified by spraying water so that the watercontent was 12.5 wt %.

The obtained expanded cut midribs (after drying) of Examples 7 and 8were stored (matched) in a constant-temperature and constant-humiditychamber at a temperature of 22.0° C. and a relative humidity of 60% fora week, thereby obtaining an equilibrium water content. After that, thefilling capacity was measured by the same method as in Examples 1 to 6described above. Also, the filling capacity of the re-humidifiedexpanded cut midribs was measured by the same method as in Examples 1 to6 described above.

In addition, the water content of the expanded cut midribs (afterdrying) was obtained by the same method as in Examples 1 to 6 describedabove.

Table 2 below shows the results.

TABLE 2 Superheated water Water content (wt %) of shredded midribsBulkiness (cc/g) vapor temperature During After After After After duringdrying (° C.) humidification drying re-humidification dryingre-humidification Example 7 270 39.3 4.7 12.5 7.4 7.0 Example 8 250 39.38.1 12.5 6.9 6.6

As shown in Table 2, in each of Examples 7 and 8 in which the humidifiedcut midribs were wetted with the water vapor stream at a temperature of125° C. before being dried with the superheated water vapor stream, andwere re-humidified after being dried, the filling capacity decreased byonly about 4% from that of the dried cut midribs (beforere-humidification).

The filling capacity of the re-humidified cut midribs of each ofExamples 7 and 8 as described above was higher than that of the expandedcut midribs (after drying) of Example 3 as a comparative example. Whenexpanding the cut midribs in order to obtain a water content of 12 wt %,therefore, the filling capacity can significantly be improved inExamples 7 and 8 in which the humidified cut midribs were wetted withthe water vapor stream before being dried with the superheated watervapor stream, and the water content was set at 12 wt % byre-humidification after drying, when compared to the method of settingthe water content at 11 wt % by only drying the humidified cut midribsas in Example 3.

Also, the comparison of the filling capacity of the re-humidified cutmidribs of each of Examples 7 and 8 with that of the expanded cutmidribs of Example 1 reveals that the filling capacity of there-humidified cut midribs of each of Examples 7 and 8 was higher thanthat of the expanded cut midribs of Example 1 (see Table 1) in which thehumidified cut midribs were dried to have a water content of 5.4 wt % byonly the drying process. This demonstrates that when wetting thehumidified cut midribs with a water vapor stream at a predeterminedtemperature before drying the humidified cut midribs with a superheatedwater vapor stream as in the present invention, the filling capacity canbe improved, even when re-humidification of increasing the water contentwas performed after drying, more significantly than that in theconventional method of performing only the drying process on thehumidified cut midribs.

1. A tobacco material expansion method comprising the steps of: wettingand swelling a tobacco material by bringing the tobacco material intocontact with a water vapor stream at 100 to 160° C.; and drying thewetted swelled tobacco material by bringing the tobacco material intocontact with a superheated water vapor stream at a temperature higherthan that of the water vapor.
 2. The tobacco material expansion methodaccording to claim 1, wherein the tobacco material before contacting thewater vapor stream is humidified to 15 to 50 wt %.
 3. The tobaccomaterial expansion method according to claim 1, wherein the wettedswelled tobacco material has a water content equal to or higher by notmore than 5 wt % than that of the tobacco material before contacting thewater vapor stream.
 4. The tobacco material expansion method accordingto claim 1, wherein the step of wetting and swelling is performed byrotating the tobacco material together with the water vapor stream. 5.The tobacco material expansion method according to claim 4, wherein aresidence time during the rotation is 0.5 to 5 s.
 6. The tobaccomaterial expansion method according to claim 1, wherein the tobaccomaterial is re-humidified after the step of drying.
 7. The tobaccomaterial expansion method according to claim 6, wherein there-humidification is performed by spraying water against the tobaccomaterial.
 8. The tobacco material expansion method according to claim 6,wherein the re-humidification is executed on the tobacco material havinga water content reduced to not more than 10 wt % in the drying.
 9. Thetobacco material expansion method according to claim 1, wherein thetobacco material comprises cut midribs.
 10. A tobacco material expansionapparatus comprising: a first cyclone including an inlet, an exhaustport, and an outlet; a first supply-side duct connected to the inlet ofthe first cyclone; a first exhaust-side duct connected to the exhaustport of the first cyclone; a first water vapor supply unit connected tothe first supply-side duct; a first tobacco material supply unitconnected to the first supply-side duct positioned between a connectingportion of the first water vapor supply unit and the inlet of the firstcyclone; a second cyclone including an inlet, an exhaust port, and anoutlet; a second supply-side duct connected to the inlet of the secondcyclone; a second exhaust-side duct connected to the exhaust port of thesecond cyclone; a heating member placed in the second supply-side duct;a second water vapor supply unit connected to the second supply-sideduct positioned downstream of the heating member; a second tobaccomaterial supply unit connected to the second supply-side duct positionedbetween the inlet of the second cyclone and the heating member; and aconveyor member configured to convey the tobacco material dischargedfrom the outlet of the first cyclone to the second tobacco materialsupply unit.
 11. The tobacco material expansion apparatus according toclaim 10, wherein a first circulation duct is formed by connecting thefirst supply-side duct and first exhaust-side duct connected to thefirst cyclone, a second circulation duct is formed by connecting thesecond supply-side duct and second exhaust-side duct connected to thesecond cyclone, and the first circulation duct positioned near theexhaust port of the first cyclone and the second circulation ductpositioned near the exhaust port of the second cyclone are connected bya connection duct.
 12. The tobacco material expansion method accordingto claim 2, wherein the tobacco material comprises cut midribs.
 13. Thetobacco material expansion method according to claim 3, wherein thetobacco material comprises cut midribs.
 14. The tobacco materialexpansion method according to claim 4, wherein the tobacco materialcomprises cut midribs.
 15. The tobacco material expansion methodaccording to claim 5, wherein the tobacco material comprises cutmidribs.
 16. The tobacco material expansion method according to claim 6,wherein the tobacco material comprises cut midribs.
 17. The tobaccomaterial expansion method according to claim 7, wherein the tobaccomaterial comprises cut midribs.
 18. The tobacco material expansionmethod according to claim 8, wherein the tobacco material comprises cutmidribs.